Process for the continuous production of lead oxides in the dry state



G SHIMADZU Dec. 25, 1934.

PROCESS FOR THE CONTINUOUS PRODUCTION OF LEAD OXIDES IN THE DRY STATE Original Flled p il 7, 1926 INVENTOR 6. 5/727776431 W Patented Dec. 25, 1934 PATENT OFFICE PROCESS FOR/THE CONTINUOUS PRODUC- TION STATE OF LEAD OXIDES IN THE DRY Gonzo Shimadzu, Kyoto, Japan Original application April 27, 1926, Serial No.

104,999, now Patent No. 1,896,020. Divided and this application August 5, 1931, Serial No.

11 Claims. (01. 23-146) This invention relates to a process for the continuous production of lead oxides, the object of the invention being to obtain such oxides in the form of the powders most suitable for use in storage batteries and paints and in a dry state, and is a division of my application Ser. No. 104,999 now Patent No. 1,896,020 issued January 31, 1933. The invention involves the subjection of pieces of metallic lead maintained in a state of agitation to artificially supplied atmospheric air or other oxidizing gas whereby a film or coating of oxide will be formed on the pieces, the formation of the film or coating being augmented without fusion of the metal by the heat generated in the principle reaction between metallic lead and the oxidizing gas and by the frictional heatcreated through rubbing of the pieces one against the other, thisrubbing action causing also abrading oil as a fine powder of the oxidethus produced,

- and the oxidizing gas or a partthereof being also :heat generated by the reaction itself and also by the friction set upowing to the rubbing of the pieces one against the other. coating is of a comparatively brittle nature and utilized to carry off the powder for collection and further treatment if needs be.

Broadly the apparatus of the inventioncomprises a vessel adapted to be rotated, means for 1 feeding pieces of metallic lead thereto while the vessel is rotating, and meansfor artificially supplying atmospheric air or other oxidizing gas to I the interior of the vessel in such a manner as to contact with the surfaces of the piecesof-lead to oxidize the same and to take up and convey the formed oxide powder as it is abraded by the rubbing action of the pieces against each other to a collector and ore filter device.

In the appended drawing, I have shown anadvantageous form of apparatus which represents an oxidizing chamber in horizontal section and i an elevation with parts broken away of a dust catching tower.

In the drawing, a denotes a drum which for '40 the purpose of permitting rotation is provided with trunnions b, I) supported by bearings c, c. The trunnion b is also journalledin a bearing 0 which is so designed as to form a casing for a worm-wheel d worm d coupled to a suitable source of power.

The trunnion b is hollow and its interior is provided with helical grooves j which as the trunnion rotates function-as a screw conveyor f and'which is supplied with pieces of lead by an automatic feeder e. Trunnion b conveys the pieces C to the drum a into which they fall at f.

Arranged axially in the hollow trunnion b is a stationary pipe 9 which extends into the drum a i and is provided with downwardly directed branch pipes gf which may be provided at their ends,

. of the same volume of water.

with nozzles g. The pipe g serves tosupply at mospheric air or other oxidizing gas under relatively high pressure from a suitable source tothe interior of the drum whilst the latter is rotating. The air or gas issuing from the nozzles g impinges 5 upon the lead pieces in thedrum and acts primarily to cause a coating or film of oxide to be formed thereon. The trunnion b' is also hollow and the inner end of the supply pipe g is provided with a nozzle g so arranged with respect to the 10 .interior of the. trunnion b as to form an ejector or exhauster for the drum (1.

The oxide which in fact is a sub-oxide is formed on the pieces principally by the action of the oxidizing as thereon as has been explained, the 15 gas acting'c'ontinuously on the surface of the pieces which are maintained in a state of agitation owing to the rotation, of the drum so that all the pieces-are properly subjected to the oxidizing action. This oxidation is aided by the.,20

The oxide film or the-continual rubbing of. the pieces together, due -25 ,to the rotational motion of the drum a, causes thisfilm or coating-to be abraded off as a suboxidepowder, thus exposing fresh surfaces of metallic lead to the action of the oxidizing gas and theotherconditions which augment the for- 30 'mation of the oxide film. This abrading off or removal of the suboxide coating from the pieces of metallic lead is also caused in part by the impinging of the air from jets g on the surfaces of the pieces of metallic lead. The air which is fed 35 through pipe 9 to the nozzles g at relatively high pressure leaves the nozzles at a velocity sumciently high to blow any oxide from those pieces of lead on which the air impinges. The combined' rubbing action of the pieces and action of 0 the jets of air upon the pieces of metallic lead provides a very efiicacious means of reducing the oxide to a remarkably fine powder, so fine in fact that from tests made it has been proved that the weightof a given volume of the powder is only 45 from one third to one tenth of the weight of the same volume of metallic lead or less of the weight As a further proof of its fineness it is found that the sub-oxide powder will readily convert to litharge in the 50 presence of an oxidizing agent by spontaneous oxidation after the application of initial heat. That is to say, if the heat of a match for example be applied momentarily to a quantity of the pow- .der, the combustion will proceed of its own accord until all the powder has been converted to litharge.

The suboxide which is formed in my machine in the above described manner is a very unstable fine powder. It is essential that it be removed from the mill in which it is formed immediately after it has been ground or blown from the lumps of lead. Otherwise if it is permitted to remain within the mill for any appreciable length of time it will go over to litharge in as much as the temperature within the mill is sufficiently high and there is a plentiful supply of air present. In the arrangement shown the powder is removed substantially instantaneously after formation by the currents of air issuing from jets g which penetrate the entire mass of lead and which leave the mill through trunnion b carrying with it the formed powder. As will be noted, the interior of trunnion b is flared from the drum to form a nozzle which, combined with the action of the air issuing from jet 9 functions as an ejector to aid in the rapid removal of said powder. A chamber h is connected near its upper end to the hollow trunnion b and acts to collect the powdered oxide or a portion of it issuing from the trunnion. This chamber h is provided with a plurality of vertical bars h which act as a screen or sieve to break down the conveying action of the ejector by impingement of the particles there against so that the particles will fall into the bottom of the chamber and accumulate therein as indicated at A. The sub-oxide powder may be removed as such from the chamber 11 at convenient intervals. 7

Frequently it is desirable that the product be in the form of litharge rather than suboxide. With the construction shown, the suboxide powder may be readily converted to litharge before removal from the container h. The advantage of converting the powder to litharge in this manner is that the conversion will be complete and the product will be uniform throughout due to the fact that the air within the chamber h is in heated condition and while so heated it has ready access to the powder as it falls on the pile A. Were the suboxide powder first permitted to accumulate in a pile and then oxidized it would be found that the product would not be uniform but that a large portion on the inside of the pile to which the air does not have ready access would remain in the suboxide state. To start the oxidation it is necessary to apply external heat to the product but once started the heat generated by the reaction will be sufficient to oxidize all of the powder which is thereafter formed in the mill and delivered to the chamber It.

Any powder intermingled with gas that passes through the screen h is transferred to a bag room or filter tower i where it is finally separated from the gas. This tower is provided with filter bags of suitable material such as silk which are subjected externally to a rarefied atmosphere or vacuum created in the upper part of the tower by means of the exhauster J. By this means the gas is drawn through the bags leaving the powder on the interior surface thereof from whence it falls and is collected at the bottom of the tower as indicated at B. Here again the suboxide powder may be removed as such at convenient intervals or first converted into litharge.

It will be appreciated that if found desirable a plurality of filter towers may be provided in series whereby the extracted gas may be subjected to further filtration to ensure complete separation of powder. It will also be appreciated that the provision of an initial separator h followed by a filter or filters is not essential to the carrying out of the invention. In some cases it might be found that the separator It could be dispensed with in which case the filter stage could be coupled direct to the drum. Again, the separator might in some instances be used without a filtration stage. I reserve to myself the right to such modification and others that are obvious in the construction and assembly of the apparatus.

Having now described my invention, what I claim as new is:

l. The method of manufacturing litharge which consists in tumbling in a rotatable vessel pieces of metallic lead and simultaneously supplying an oxidizing gas to said vessel to form a coating of suboxide upon the surfaces of said pieces, abrading and simultaneously removing said suboxide coating from said pieces while dry, delivering said suboxide from said rotatable ,vessel to a separate chamber and converting said suboxide to litharge within said chamber.

2. The method of manufacturing litharge which consists in feeding pieces of metallic lead to a rotatable vessel causing a plurality of jets of oxidizing agent to impinge upon said metallic lead pieces to oxidize the surfaces thereof to suboxide while 'dry, rotating said vessel to abrade suboxide from said metallic lead pieces, blowing said sub- 1 oxide from said vessel to an enclosed chamber and oxidizing said suboxide within said chamber to litharge.

3. 'Ihe method of manufacturing litharge which consists in introducing into a rotary mill pieces of metallic lead, simultaneously rotating the mill and forcing air directly against the lead during the rotating process to oxidize the surface of the lead pieces to PbzO while dry and to immediately remove the oxidized lead from the surfaces of the lead pieces, blowing the formed oxidized lead powder while still mainly in the form of Pb2O from the mill and further oxidizing the powder to litharge.

4. The process of making lead powders of a composition containing a higher oxygen content than lead suboxide, such as litharge, which comprises pulverizing in a dry state in a. rotating mill metallic lead lumps into a fine powder composed mainly of lead suboxide and immediately removing the powder from the lumps and subsequently oxidizing the separated suboxide powder into the litharge or powder containing the higher oxygen content by igniting the powder.

5. The method of manufacturing a comparatively stable lead oxide, such as litharge, from lead lumps in a dry state, comprising, rotating the lead lumps in a mill and simultaneously causing an oxidizing gas to pass through the mill in contact with the lumps to oxidize their outer. surfaces only to an oxide having a comparatively lower oxygen content than said stable oxide, continuously removing the oxide while in its dry and unstable state to expose the metallic lead to said gas to produce more unstable oxide and immediately oxidizing the produced lead oxide, having the lower oxygen content than litharge, to finally produce the litharge.

6. The method of manufacturing a product mainly composed of litharge, which consists in rotating in a vessel pieces of metallic lead and simultaneously impinging against said pieces of lead an oxygenized gas to form a coating of lead suboxide upon the surface of said pieces, abrading while dry said suboxide coating from said pieces by the action of said gas and by mutual attrition, blowing said suboxide from said rotatable vessel to a filtering chamber to separate the conveying gas and suboxide and converting said suboxide to litharge by starting its ignition, said ignition being kept up by self-generated heat.

7. The method of manufacturing litharge which consists in feeding pieces of metallic lead to a rotatable vessel, causing a plurality of jets of an oxidizing gas to impinge upon said metallic lead pieces to oxidize the surfaces thereof to suboxide, simultaneously rotating said vessel to abrade the suboxide from said metallic lead pieces while dry, blowing said suboxide from said vessel to a gas filtering chamber to separate the suboxide from the conveying gases and oxidizing the said suboxide within said chamber to litharge.

8. The process of making lead powder of a composition containing a higher oxygen content than PbzO, which comprises pulverizing metallic lead lumps in a tumbling mill while simultaneously supplying the mill with an oxygen containing gas to form PbzO on the surface of the lead lumps, removing the Pb2O immediately after it is formed from the lead lumps and subsequently further oxidizing the Pb2O to form the composition containing the higher oxygen content.

9. The process of making lead powder of a composition containing a higher oxygen content than PbzO, such as litharge, which comprises pulverizing in a dry state and in a rotating mill metallic lead lumps into a fine powder and removing the powder from the lumps as soon as formed and while in a dry state to prevent ac cumulation of the powder on the lumps and then further oxidizing the powder spontaneously by its own heat into a powder of a higher oxygen content than PbzO.

10. The process of making lead powder of a composition containing a higher oxygen content than PbzO, such as litharge, which comprises pulverizing in a dry state and in a rotating mill metallic lead lumps into a powder so fine that the weight of a given volume of the powder is only from one-third to one-tenth of the Weight of the same volume of metallic lead and further oxidizing the powder by heat spontaneously generated therein into a powder composed principally of litharge.

11. The process of manufacturing a comparatively stable lead oxide, consisting principally of litharge, from lead lumps in a dry state, comprising rotating the lead lumps in a mill and simultaneously causing an oxidizing gas to pass through the mill in contact with the lumps to oxidize their outer surface only to an oxide having a comparatively lower oxygen content than said stable oxide, continuously removing the oxide while in its dry and unstable state to expose the metallic lead to said gas to produce more unstable oxide and immediately oxidizing the produced lead oxide, having the lower oxygen content than litharge to finally produce a powder consisting principally of litharge.

GENZO SHIMADZU. 

